Carbon Monoxide Poisoning, Adult and Pediatric
Carbon Monoxide Poisoning, Adult and Pediatric

Work up:

  • Carboxyhemoglobin (COHb) level via arterial or venous sample.
  • Blood gas to assess for degree of metabolic acidosis.
  • ECG for patients ≥65 years and patients with chest pain.
  • Pregnancy tests for women of childbearing age.
  • Cyanide level for those with fire exposure.

If intentional, consider toxicology screen.

Consider CNS imaging to assess for other causes of altered mental status.

Urine Pregnancy, Urine
ISTAT Venous Blood Gas, Serum
Urine Toxicology, Urine
Carboxyhemoglobin, COHgb, serum
Cyanide, serum

If after initial evaluation with labs, the patient does not meet criteria for carbon monoxide poisoning, consider work up for other etiologies. If not already obtained, consider CNS imaging.

Initiate oxygen therapy: Immediately apply high-flow 100% oxygen via nonbreather face mask.

Inclusion Criteria
  • Suspected or confirmed carbon monoxide poisoning
  • Symptoms of carbon monoxide poisoning
  • Known carbon monoxide exposure
Exclusion Criteria
  • None

Severely altered patient?

Intubate and provide 100% oxygen.

Red Flag Symptoms:

  • Lack of fever.
  • Known exposure.
  • Multiple patients presenting together with the same symptoms.

(Adapted from CDC’s “Clinical Guidance for Carbon Monoxide (CO) Poisoning After a Disaster.”)

Intentional poisoning?

Treatment of Mild to Moderate Symptoms: Continue high-flow oxygen therapy with 100% oxygen via nonrebreather mask for 6 hours or until symptoms resolve.

Treatment of Serious Symptoms: Physician can consider hyperbaric oxygen therapy in patients with severe manifestations of carbon monoxide poisoning. Current evidence for its use is controversial.

Back to baseline?

Obtain a history and physical, including:

  • Symptoms.
  • Duration of exposure.
  • Time since exposure.
  • Source of exposure.
  • If others were exposed.
  • Past medical history including current pregnancy, history of sickle cell, chronic cardiac or pulmonary conditions.


  • Can be made on history of exposure and symptoms alone.
  • Or based on carboxyhemoglobin (COHb) level:
  • >2.5% in non-smokers
  • >10% in smokers

*Note: degree of COHb level elevation does not correlate with symptoms or sequelae.

Standard pulse oximetry (SpO2) CANNOT screen for CO exposure, as it does not differentiate carboxyhemoglobin from oxyhemoglobin

Signs of Serious Acute Poisoning:

  • Loss of consciousness
  • Ischemic cardiac changes
  • Neurologic deficits
  • Severe metabolic acidosis (pH <7.1)
  • COHb >25%

Requires admission for continued therapy and monitoring. May require OT and PT involvement to assess for new and ongoing limitations and therapy needs.

Admit to Floor

Requires psychologic evaluation and clearance prior to discharge. May require psychiatric hold placement.

Can discharge home if back to baseline. Follow up in 1-2 months – if persistent neurocognitive symptoms at that time, recommend referral for formal neuropsychological assessment.

Prevention is Key:

  • Discuss importance of household carbon monoxide detectors and strategies to reduce risk of exposure.

Helpful Online Resources:

Symptoms of Carbon Monoxide Poisoning:

Mild symptoms include:

  • Tension headache
  • Dizziness
  • Nausea and vomiting

Severe symptoms include:

  • Vital sign instability: tachycardia, tachypnea, hypotension
  • Metabolic acidosis
  • Dysrhythmias
  • Myocardial ischemia or infarction
  • Pulmonary edema
  • Neurologic findings:
  • Irritability
  • Impaired memory
  • Cognitive and sensory disturbances
  • Ataxia
  • Altered mental status
  • Loss of consciousness
  • Seizures
  • Death

Pediatric Symptoms: Nonverbal children may exhibit fussiness or difficulty feeding. They are often symptomatic prior to adults with similar exposure due to their increased minute ventilation.

If signs of ischemia on ECG, obtain cardiac enzymes and consult Cardiology.

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